A student raises her grade average from a 75 to a 90. what was the percent of increase in the student's grade average? round your answer to the nearest tenth of a percent, if necessary. (1 point) 20% 16.7% 8.3% 15% 2. beanbag chairs that normally sell for $36.50 are on sale for $32.12. find the percent of discount. round your answer to the nearest tenth of a percent, if necessary. (1 point) 88% 12% 13.6% 3.38% 3. last year, austin, texas received 23.5 inches of rainfall. this year, austin received 21.2 inches of rainfall. find the percent of decrease in the number of inches of rainfall. round your answer to the nearest tenth of a percent, if necessary. (1 point) 2.3% 9.8%

here are some formulas...
percent increase = (new number - original number) / original number...* 100
percent decrease = (original number - new number) / original number...* 100
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a student raises her grade from a 75 to a 90....since it is going from a smaller number to a larger number, u have an increase
percent increase = (90 - 75) / 70....* 100
                           =   15/70   * 100
                           = 0.2142 * 100
                           = 21.42 rounds to 21.4%  increase
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36.50 on sale for 32.12...since it goes from a larger number to a smaller number, u have a decrease
percent decrease = (original number - new number) / original * 100
                             = (36.50 - 32.12) / 32.12...* 100
                             = 4.38 / 32.12...* 100
                             = 0.1363...* 100
                             = 13.63 rounds to 13.6% decrease
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23.5 to 21.2......this is a decrease
percent decrease = (original number - new number) / original...* 100
                            = (23.5 - 21.2) / 23.5....* 100
                            = 2.3 / 23.5....* 100
                            = 0.0979 * 100
                            = 9.79 rounds to 9.8% decrease